The storage capacity of the stacks of modern libraries are rapidly being exhausted for the reason that the stacks and aisles are fixed, the storage space is fixed and yet publishers continue to turn out books year after year.
Thus many libraries, and other institutions, or businesses which must store an inventory in a fixed space have turned to mobile shelving.
Exemplary of one form of such mobile, or compact, storage is U.S. Pat. No. 3,427,085 to Staller of Feb. 11, 1969 in which a cluster of juxtaposed, elongated side by side, upstanding stacks of shelves are mounted to roll on laterally extending guide tracks, by a manual sidewise push or a front end wall handle. A similar compact storage system is disclosed in U.S. Pat. No. 3,801,176 to Higbee of Apr. 2, 1974 wherein a similar cluster of open elongated baskets are mounted to move laterally on a pair of guide tracks, to segregate one of the baskets, by manual means.
In a more sophisticated form, compact shelving for libraries is taught wherein the elongated stacks are moved sidewise on sidewise, or lateral, tracks by means of the mechanical advantage of a lever on the front end as in U.S. Pat. No. 3,567,299 to Lundquist of Mar. 2, 1971. A handwheel, rotatable in a plane parallel to the front end, to turn wheels rotating in a parallel plane is taught in U.S. Pat. No. 3,944,309 to Taniwaki of Mar. 16, 1976. The stacks are connected by releasable links and moved sidewise on sidewise extending tracks by a fluid actuated piston and cylinder in U.S. Pat. No. 3,080,204 to Lindhgren of Mar. 5, 1963.
A still more sophisticated, costly and complicated form of compact shelving is disclosed in the following patents:
U.s. pat. No. 3,168,361 to Naito of Feb. 2, 1965 PA1 U.s. pat. No. 3,535,009 to Cain of Oct. 20, 1970 PA1 U.s. pat. No. 3,615,122 to Naito of Oct. 26, 1971
U.S. Pat. No. 3,967,868 to Baker, Jr., of July 6, 1976 in all of which, each stack is provided with its own electric motor drive so that a single longitudinally extending aisle may be created between two adjacent stacks of the cluster to give access to open side shelves thereon.
A disadvantage of all such sidewise movable stacks, mounted on sidewise extending tracks, whether manually or power moved is that at least one stack width of track must project beyond the cluster to be tripped over, or requiring that the entire track be embedded in the floor, or that a raised floor be installed around the tracks, both expensive alternatives. Another disadvantage, is that only one longitudinally extending space for access to the stacks, is possible at a time, in conventional such installations, thus requiring others to wait until a book has been selected and the stacks again separated at a different space.